Eye testing device



June 13, 1939. c K SCHUBERT 2,161,936

EYE TESTING DEVICE Filed Sept. 12, 1936 In uentor fczg ez' Attorneys Patented June 13, 1939 UNITED STATES PATENT OFFICE 2 Claims.

The present invention relates generally to new and useful improvements in eye testing devices and particularly to what are commonly known by opticians and oculists in the profession 6 as cross cylinders.

The usual cross cylinder is a compound lens having a minus strength in one principal meridian exactly equal to a plus strength in the opposite principal meridian. It is made by grinding a minus sphere combined with a plus cylinder whose strength is twice that of the sphere. The cross cylinder is placed in a circular mount, the handle of which is at 45 degrees with the two opposite principal meridians. This alignment must be accurate or the testing is inaccurate. The cross cylinder is held in front of the trial frame and is flipped so that the patient has the choice between looking through its two surfaces. The power of the astigmatic lens (that is, the cylinder), has been previously determined, the axis only being in doubt. The axis of the cross cylinder which is exactly between the two principal meridians is placed in the axis of the cylinder. The patient looks at the smallest line on the chart that he can still see, and states that it looks a little more blurred or a little clearer. The operator then reverses the surfaces, keeping the axis the same. If the patient sees any diiference in the clarity of the line he is observing the 30 axis is not correct. The cylinder and cross cylinder, always being kept in the same axis, are rotated until there is an equal blurring of the line as the operator flips the two surfaces of the cross cylinder in front of the patient. By this 35 procedure the patient must remember what effect each position of the cross cylinder has on the blurring or clearing of the line on the chart and must tell when he thinks they are the same before an accurate reading of axis can be attained. The proper axis of the cross cylinder must at all times be parallel to the axis of the cylinder as it is turned.

It may thus be seen from a description of an ordinary cross cylinder that there is an elapse of time between the view of the blurred or clear line or field and a view of the same blurred or clear line or field with the other side of the cross cylinder. In other words, the patient must make a comparison of one metal and one physical image or he must remember whether what he saw a second before is the same as what he sees at the moment. It is the primary object of the present invention to provide what will be referred to as a split cross cylinder wherein the two images will be placed simultaneously before the patient so that an actual physical comparison may be made. Other objects of the invention are to provide a testing instrument of the aforementioned character which will be simple in construction, compact, highly eflicient and reliable in use and which 5 may be manufactured at low cost.-

All of the foregoing and still further objects and advantages of the invention will become apparent from a study of the following specification, taken in connection with the accompanying drawing wherein like characters of reference designate corresponding parts throughout the several views and wherein:

Figure 1 is an elevational view of an embodiment of the invention.

Figure 2 is a sectional view through the instrument, taken substantially on the line 22 of Figure 1.

Referring now to the drawing in detail, it will be seen that the embodiment of the invention which has been illustrated comprises an annular frame I which is mounted on one end of a suitable handle 2. Mounted in the frame I is a lens which is designated generally by the reference numeral 3,

The lens 3 may be a conventional cross cylinder lens of any power but which has been bisected along a line half way between its minus and plus axes. This line of division is indicated at 4. It will be noted that the lens is thus divided into half sections 5 and 6. One half of the lens thus divided is so reversed that the plus portion and the minus portion are in opposition. The two halves are then secured in this relation along the line of severance by suitable means in a manner to produce a substantially invisible joint. With this construction and arrangement when the patient looks through one half of the bisected lens he is conscious of a certain visual effect while looking at a chart, while if he looks through the other half of the bisected portion he receives the same effect as if the first portion had been flipped or turned so that the opposite surface would be toward him. It will therefore be seen that the necessity of flipping the lens by the operator in front of the cylinder which he has on the patient to be tested is obviated. The patient looks through the split cross cylinder at a chart at any distance in front of him and upon which charts a line or lines of letters, figures, numbers, etc., of any size are placed at any axis. The line or lines of letters, figures, numbers, etc., at which the patient looks will be bisected by the split cross cylinder into one blurred and one clear half, or two equally blurred halves dependent 55 on rotation in and out of axis of the cylinder and split cross cylinder. The proper astigmatic axis will have been reached when the two halves of this line or lines in any meridian will be of equal blurring.

It is believed that the many advantages of a testing instrument constructed in accordance with the present invention will be readily understood, and although a preferred embodiment of the device is as illustrated and described, it is to be understood that changes in details of construction maybe resorted to which will fall within the scope of the invention as claimed.

Having thus described the invention what is claimed is:

1. A cross cylinder of the character described, said cross cylinder comprising a transparent V circular body, a frame on said body and including a handle projecting radially therefrom and aligned with a diameter of said body, said body cular body, a frame on said body and having a' handle projecting radially therefrom and aligned with a diameter of said body, the portions of said body lying on opposite sides of said diameter being formed with cross cylinder lens portions, each of said lens portions being provided with a plus area and a minus area, whereby said diameter lies halfway between the plus areas and '16 minus areas, said lens portions being arranged with the plus areas adjacent to each other and V with the minus areas adjacent to each other.

CLARENCE SCHUBE-RT. 

